In WO09153184, a low dosage or concentrated aqueous laundry detergent liquid is used to reduce the amount of chemicals per wash. This is achieved, without loss of detergency, by reduction of the amount of surfactant used per wash and use, in its place, of highly weight efficient enzymes and polymers to boost detergency on everyday dirt and stains. Preferred compositions use enzymes and combinations of high levels of ethoxylated polyethyleneimine polymer and polyester soil release polymer.
Low dosage compositions formulated this way are suitable for laundry and hard surface cleaning applications. Both the removal of the surfactant and the use of cleaning polymers like ethoxylated polyethylene imine and polyester soil release polymers cause a drop in viscosity of the liquid. We have found that consumers desire that the pour viscosity of a concentrated liquid should be at least as high as a conventional dilute liquid and possibly even higher so that they have a reason to believe that the liquid contains the same cleaning power as a higher dosage detergent liquid with higher surfactant levels and possibly without such high levels of viscosity reducing polymer additives.
It is also desirable to be able to include particulate materials into such liquid detergent compositions, for example encapsulated perfume or visual cues. Advantageously, the liquid should have rheology that provides a yield stress (also known as critical stress) so that the particles remain stably suspended and dispersed and yet the composition may be poured from a bottle or dispensed by a suitable spray or pump mechanism.
Crosslinked hydrophobically modified copolymers are exemplified in US2004 063855 (Rohm and Haas) and where such a polymer was used at 1.5 wt % with a specified clay and 22.3 wt % mixed surfactant. It is stated that the composition synergistically increases the low shear (e.g., suspending or stabilizing) viscosity significantly while having little effect on the mid-shear (pouring) viscosity. We have found that these types of acrylates copolymers give an undesirably high pour viscosity if they are used at a high enough level to provide a suspending rheology. Alternative prior art copolymers do provide the shear thinning behaviour required for suspending but do not on their own provide the pour viscosity that is desired by consumers. This can lead to the need to use a second rheology modifying material in conjunction with the acrylate copolymer. This is an unwanted complication.
It is an object of the present invention to provide detergent compositions with an alternative copolymer that increases the pour viscosity while providing the required rheology for suspending. The increase in pour viscosity is useful to counteract the effect of inclusion of certain polymers that have the effect of reducing the pour viscosity of the composition. The copolymers may be utilised in compositions comprising linear alkyl benzene sulphonate anionic surfactant which is the workhorse surfactant found in most laundry and dish wash compositions.